The present invention relates to an improved electrical contact for systems having a track-mounted, movable carriage in which power, control and/or monitored information is transmitted to and/or received from the movable carriage.
Moving electrical contacts are often used in systems that include an electrically-powered carriage that moves along a track. The movable carriage may be controlled by electrical signals transmitted to the movable device from a remote location. Also, the movable device may transmit information in the form of electrical signals to the remote location.
A system that uses moving electrical contacts to transmit power, control and/or monitored information is disclosed in U.S. Pat. No. 5,241,380 issued to Benson. Benson discloses a track mounted camera system adapted for surveillance of a large area. The system includes a carriage that is driven by a drive assembly longitudinally along a track assembly that is positioned along a selected path. A pair of electrically conducting signal rails are mounted adjacent and parallel to the track to provide power to the electric motor. Video cameras are mounted to the carriage for monitoring selected portions adjacent to the path. Output signals from the cameras are transmitted on the signal rails to a remote monitoring location. Control signals for controlling placement of the carriage along the track are also transmitted on the signal rails to the carriage.
The signal rail is a pair of spaced apart, electrically isolated conductors comprising cylindrical, copper tubing mounted and supported within semi-cylindrical grooves of an isolation block made of electrically insulating material. Each conductor is in slidable contact with at least one corresponding isolated slidable electrically conductive brush along the length of the rail. Each brush is biased against the respective conductor by a spring that is inserted within a support also made of electrically insulating mnaterial. The brushes are mounted to a support platform that is connected to the carriage thereby providing a moving electrical contact between the carriage and the signal rails.
Another prior art moving electrical contact is disclosed in the track-mounted surveillance system described in FIGS. 1, 1a. A carriage 15 carrying cameras 17 moves by wheels 10 attached thereto. The moveable electric contact consists of a pair of electrically conductive graphite wheels 10 which are mounted on a moveable carriage 15 and form an electrical connection with the carriage. The graphite wheel pair is in electrical contact with a pair of signal rails that extend longitudinally along the track (not shown). As the carriage moves along the track, the graphite wheel pairs provide an electrical connection between the carriage and the signal rails.
While the prior art moveable electric contacts worked for their intended purposes, a significant drawback of these prior art contacts is that they generate acoustic noise levels that are unacceptable for particular applications. For instance in track-mounted surveillance systems, high acoustic noise levels generated by the moving electrical contacts may enable people in the monitored area to determine the location of the carriage along the track. Another problem with the prior art contacts is that they are prone to wear and tear from continued used which causes the electrical connection to become unreliable.
By constructing moving electrical contacts in accordance with the present invention, undesirable acoustical noise is significantly reduced, a stable and reliable electrical connection is maintained and the life expectancy of the contact is significantly increased.